The invention relates to flow control and isolation in a wellbore.
One of the operations performed in completing a wellbore is perforating one or more formation zones to allow hydrocarbons to flow into the wellbore. Typically, a gun string is lowered to the desired well interval and fired to create openings in the surrounding casing or liner and to extend perforations into the surrounding formation. Another operation that may be performed includes sand control in zones that may produce sand or other contaminants. One technique for performing sand control includes gravel packing.
To avoid having to use kill fluids after a formation has been perforated or gravel packed, formation isolation valves (FIVs) or other types of isolation devices may be used. An FIV may include a ball valve, a sleeve valve, a flapper valve, or some other valve. In one application, an FIV may be closed to allow a gun string or gravel pack service tool to be pulled out after perforation or gravel packing has been performed. Closing of the FIV also allows the upper part of a wellbore to be further completed. FIVs may be operated with a number of different mechanisms, including a shifting tool, a tubing pressure-activated mechanism, or a control line pressure-activated system.
To provide fluid loss and well isolation control in a well with multiple zones while an upper part of the well is being completed, multiple isolation devices may be used for each respective zone. Examples of completion operations in the upper part of the well include installing the following components: setting a production packer, installing downhole monitoring and control modules (such as those associated with an intelligent completion system), installing a subsurface safety valve (SSV), inserting a production tubing, and installing other components.
However, adequate well isolation control may not be provided with use of individual isolation devices, particularly if the upper completion string includes components run outside the production tubing, such as cables, control lines, and so forth. As soon as the upper isolation device is opened, the upper zone is unprotected and the well may start taking fluid. The time to complete installation of the completion string to the depth of the lower zone, especially with intelligent completion equipment, may be relatively long. If well isolation control is required, a blow-out preventer (BOP) at or near the surface may be closed. Typically, the BOP seals on the outer diameter of a production tubing. However, if cables or other components are attached to the outside of the tubing, the BOP may not seal properly. In addition, closing the BOP may damage such components attached to the outside of the production tubing.
To better provide fluid loss and well isolation control, a formation isolation dual valve (FIDV) may be used. In one example FIDV, a ball valve is used to isolate one zone and a sleeve valve is used to isolate another zone. In conjunction with an isolation packer, the FIDV provides protection for multiple zones while the upper portion of the completion string is being installed.
In a multi-zone wellbore, once an FIDV and associated components are installed, a flow control device may be run into the wellbore and installed above the FIDV to perform flow control of the two or more zones during production. However, installing a separate isolation device (e.g., FIDV) for fluid loss control and flow control device adds to the complexity of completion operations. Effectively, two sets of valves are used for each zone, one for isolation and the other for flow control. Installing the extra components adds to the time and costs of completing a well. In addition, the presence of extra components increases the likelihood that failure of some downhole component would occur, which would then require a work-over operation that typically includes pulling out the completion string, replacing the failed component, and re-installing the completion string. Such work-over operations are extremely expensive and time-consuming.
A need thus exists for an improved method and apparatus for performing flow control and isolation of a wellbore having a plurality of zones.
Various mechanisms may be used to control activation of downhole valves. Such mechanisms may be electrically-activated, pressure-activated, or mechanically-activated. Pressure activation may be accomplished by communicating pressure through a production tubing or through one or more control lines running along side the tubing. However, once production of fluids starts, communication of a desired pressure through the tubing may not be possible. Control lines may be used instead. Conventionally, separate hydraulic control lines have been used for different flow control devices. The existence of multiple control lines downhole may make installation of a completion string more difficult, which increases the costs associated with the operation of a well.
A need thus exists for a method and apparatus to reduce the number of control lines that need to be run downhole for controlling activation of downhole components, such as valves, from the well surface.